Slitherine

More units on the map, more scenarios - less turns in the game, it's probably logical. Devs don't want to bore the player...
In my mod, I'll modify some of the things you have presented here

Low-turn scenarios are more the Panzer General speed-style without these annoying kill-all objectives that take forever in OoB because of the retreat mechanic.
Sometimes it's fine to relax in scenarios with plenty turns available, but on the other hand it's maybe getting tiresome if you repeat content that requires so many turns. A mixed bag.

Yeah, mop-up-duty can be quite tiresome with OoB. And lengthy missions with sporadic or just static resitance in the later stages can be annoying, too, sometimes. "Quick and dirty" is one way to go. But I've read about good action throughout the missions in Endsieg.

Defensive scns are (often) rather short and intense - you don't want to go overboard there.

Offensive scns may have more max. turns, but they often don't go full time due to various "early victory" triggers - something that that is not so important for shorter scns where the player needs to hold out for a min. of time/turns.

DLC Sandstorm :